RICH HISTORY: The foundation of an almshouse dating to the 18th century is seen yesterday after it was discov- ered during a dig outside City Hall (above) for a renovation project. Photo: Post photos: Chad Rachman

A bit of the city’s pre-Revolutionary history peeked through when archaeologists began digging test holes around City Hall as part of a $100 million renovation project and discovered remnants of an ancient almshouse.

City officials yesterday reported artifacts of the poorhouse right behind City Hall, including what appears to be the original foundation sitting adjacent to a modern-day retaining wall.

“It’s not surprising to find remnants of historic structures,” said Amanda Sutphin, director of archaeology at the Landmarks Preservation Commission. “But to be this close to the retaining wall is a little shocking.”

She said a three-day dig uncovered hundreds of artifacts, from clay pipe stems to pottery shards to bones of butchered animals, all suspected to date from the 1700s. Tests are continuing to confirm the dates.

“There were lots and lots of bones,” Sutphin reported. “This was a pretty big institution.”

The two-story almshouse stood from 1736-1797 in an area that dates back to Dutch days and now serves as City Hall Park and includes both City Hall and the infamous Tweed Courthouse.

“In the 18th century, institutions not wanted in the center of town were placed here,” Sutphin explained.

Those ranged from army barracks to jails to powder houses.

The center of town then was further south. Minutes from the Common Council, the local legislature at the time, state that the 86-foot long almshouse served “poor needy persons, idle wandering vagabonds, sturdy beggars and parents of bastard children.”

Nineteen years ago, about a block away, workers building a new federal building unearthed the African Burial Ground, stark evidence of one of the largest urban African populations in the American colonies in the 18th century.

The skeletal remains of more than 400 men, women and children were eventually counted.

Officials intend to build a sub-cellar at the almshouse site to house new mechanical equipment for City Hall, which is undergoing a three-year renovation.